Pneumatic systems normally comprise a compressor for the compression of a fluid, air or any other gas, and a tank in connection with the compressor, and a conduit for guiding the fluid to one or more user places. Normally, the user place is an air-operated member such as an air-operated tool or an air-operated engine.
Upon the compression of air heat is generated, which in contemporary pneumatic systems, normally and generally, is transferred to the environment already before the air has reached the user place. It should be mentioned that in connection to so-called adiabatic compression (without any heat exchange with the environment, and here regarded as relevant for piston compressors, which is, a common type of compressor in this context) of air that has a temperature of 300 K and a pressure of 1 bar absolute up to 10 bar absolute, the final temperature is approximately 579 K. The volume of the air at the user site, that is by the tool has decreased with (1− 300/579)×100%=48% if the temperature at the user site has decreased to 300K. Normally, the transfer of heat to the environment is only a large loss of energy. Occasionally, the compression heat is taken advantage of for the purpose of water heating, resulting in a substantial improvement of the total economy. However, the size of the plant, that is the size of the compressor, and the capacity thereof remain the same. Furthermore, the tank that is used for the storage of air, as well as the air conduit, may be insulated to a certain degree, which is also positive for the reduction of the consumption of energy. The compressor and the tank are dimensioned with regard to the need of air at the user site and the heat losses.
There are also other losses, but the far most important source of loss is constituted by said heat loss. The heat loss effects the energy efficiency negatively. An excessive amount of energy is required for the operation of a compressor for supplying, for example, pressurised air to a tool of a certain power.